Animals are multicellular eukaryotic organisms that form the biological kingdom Animalia. With few exceptions, animals consume organic material, breathe oxygen, are able to move, can reproduce sexually, grow from a hollow sphere of cells, the blastula, during embryonic development. Over 1.5 million living animal species have been described—of which around 1 million are insects—but it has been estimated there are over 7 million animal species in total. Animals range in length from 8.5 millionths of a metre to 33.6 metres and have complex interactions with each other and their environments, forming intricate food webs. The category includes humans, but in colloquial use the term animal refers only to non-human animals; the study of non-human animals is known as zoology. Most living animal species are in the Bilateria, a clade whose members have a bilaterally symmetric body plan; the Bilateria include the protostomes—in which many groups of invertebrates are found, such as nematodes and molluscs—and the deuterostomes, containing the echinoderms and chordates.
Life forms interpreted. Many modern animal phyla became established in the fossil record as marine species during the Cambrian explosion which began around 542 million years ago. 6,331 groups of genes common to all living animals have been identified. Aristotle divided animals into those with those without. Carl Linnaeus created the first hierarchical biological classification for animals in 1758 with his Systema Naturae, which Jean-Baptiste Lamarck expanded into 14 phyla by 1809. In 1874, Ernst Haeckel divided the animal kingdom into the multicellular Metazoa and the Protozoa, single-celled organisms no longer considered animals. In modern times, the biological classification of animals relies on advanced techniques, such as molecular phylogenetics, which are effective at demonstrating the evolutionary relationships between animal taxa. Humans make use of many other animal species for food, including meat and eggs. Dogs have been used in hunting, while many aquatic animals are hunted for sport.
Non-human animals have appeared in art from the earliest times and are featured in mythology and religion. The word "animal" comes from the Latin animalis, having soul or living being; the biological definition includes all members of the kingdom Animalia. In colloquial usage, as a consequence of anthropocentrism, the term animal is sometimes used nonscientifically to refer only to non-human animals. Animals have several characteristics. Animals are eukaryotic and multicellular, unlike bacteria, which are prokaryotic, unlike protists, which are eukaryotic but unicellular. Unlike plants and algae, which produce their own nutrients animals are heterotrophic, feeding on organic material and digesting it internally. With few exceptions, animals breathe oxygen and respire aerobically. All animals are motile during at least part of their life cycle, but some animals, such as sponges, corals and barnacles become sessile; the blastula is a stage in embryonic development, unique to most animals, allowing cells to be differentiated into specialised tissues and organs.
All animals are composed of cells, surrounded by a characteristic extracellular matrix composed of collagen and elastic glycoproteins. During development, the animal extracellular matrix forms a flexible framework upon which cells can move about and be reorganised, making the formation of complex structures possible; this may be calcified, forming structures such as shells and spicules. In contrast, the cells of other multicellular organisms are held in place by cell walls, so develop by progressive growth. Animal cells uniquely possess the cell junctions called tight junctions, gap junctions, desmosomes. With few exceptions—in particular, the sponges and placozoans—animal bodies are differentiated into tissues; these include muscles, which enable locomotion, nerve tissues, which transmit signals and coordinate the body. There is an internal digestive chamber with either one opening or two openings. Nearly all animals make use of some form of sexual reproduction, they produce haploid gametes by meiosis.
These fuse to form zygotes, which develop via mitosis into a hollow sphere, called a blastula. In sponges, blastula larvae swim to a new location, attach to the seabed, develop into a new sponge. In most other groups, the blastula undergoes more complicated rearrangement, it first invaginates to form a gastrula with a digestive chamber and two separate germ layers, an external ectoderm and an internal endoderm. In most cases, a third germ layer, the mesoderm develops between them; these germ layers differentiate to form tissues and organs. Repeated instances of mating with a close relative during sexual reproduction leads to inbreeding depression within a population due to the increased prevalence of harmful recessive traits. Animals have evolved numerous mechanisms for avoiding close inbreeding. In some species, such as the splendid fairywren, females benefit by mating with multiple males, thus producing more offspring of higher genetic quality; some animals are capable of asexual reproduction, which results
Amphinase is a ribonuclease enzyme found in the oocytes of the Northern leopard frog. Amphinase is a member of the pancreatic ribonuclease protein superfamily and degrades long RNA substrates. Along with ranpirnase, another leopard frog ribonuclease, amphinase has been studied as a potential cancer therapy due to its unusual mechanism of cytotoxicity tested against tumor cells
A chordate is an animal constituting the phylum Chordata. During some period of their life cycle, chordates possess a notochord, a dorsal nerve cord, pharyngeal slits, an endostyle, a post-anal tail: these five anatomical features define this phylum. Chordates are bilaterally symmetric; the Chordata and Ambulacraria together form the superphylum Deuterostomia. Chordates are divided into three subphyla: Vertebrata. There are extinct taxa such as the Vetulicolia. Hemichordata has been presented as a fourth chordate subphylum, but now is treated as a separate phylum: hemichordates and Echinodermata form the Ambulacraria, the sister phylum of the Chordates. Of the more than 65,000 living species of chordates, about half are bony fish that are members of the superclass Osteichthyes. Chordate fossils have been found from as early as the Cambrian explosion, 541 million years ago. Cladistically, vertebrates - chordates with the notochord replaced by a vertebral column during development - are considered to be a subgroup of the clade Craniata, which consists of chordates with a skull.
The Craniata and Tunicata compose the clade Olfactores. Chordates form a phylum of animals that are defined by having at some stage in their lives all of the following anatomical features: A notochord, a stiff rod of cartilage that extends along the inside of the body. Among the vertebrate sub-group of chordates the notochord develops into the spine, in wholly aquatic species this helps the animal to swim by flexing its tail. A dorsal neural tube. In fish and other vertebrates, this develops into the spinal cord, the main communications trunk of the nervous system. Pharyngeal slits; the pharynx is the part of the throat behind the mouth. In fish, the slits are modified to form gills, but in some other chordates they are part of a filter-feeding system that extracts particles of food from the water in which the animals live. Post-anal tail. A muscular tail that extends backwards behind the anus. An endostyle; this is a groove in the ventral wall of the pharynx. In filter-feeding species it produces mucus to gather food particles, which helps in transporting food to the esophagus.
It stores iodine, may be a precursor of the vertebrate thyroid gland. There are soft constraints that separate chordates from certain other biological lineages, but are not part of the formal definition: All chordates are deuterostomes; this means. All chordates are based on a bilateral body plan. All chordates are coelomates, have a fluid filled body cavity called a coelom with a complete lining called peritoneum derived from mesoderm; the following schema is from the third edition of Vertebrate Palaeontology. The invertebrate chordate classes are from Fishes of the World. While it is structured so as to reflect evolutionary relationships, it retains the traditional ranks used in Linnaean taxonomy. Phylum Chordata †Vetulicolia? Subphylum Cephalochordata – Class Leptocardii Clade Olfactores Subphylum Tunicata – Class Ascidiacea Class Thaliacea Class Appendicularia Class Sorberacea Subphylum Vertebrata Infraphylum incertae sedis Cyclostomata Superclass'Agnatha' paraphyletic Class Myxini Class Petromyzontida or Hyperoartia Class †Conodonta Class †Myllokunmingiida Class †Pteraspidomorphi Class †Thelodonti Class †Anaspida Class †Cephalaspidomorphi Infraphylum Gnathostomata Class †Placodermi Class Chondrichthyes Class †Acanthodii Superclass Osteichthyes Class Actinopterygii Class Sarcopterygii Superclass Tetrapoda Class Amphibia Class Sauropsida Class Synapsida Craniates, one of the three subdivisions of chordates, all have distinct skulls.
They include the hagfish. Michael J. Benton commented that "craniates are characterized by their heads, just as chordates, or all deuterostomes, are by their tails". Most craniates are vertebrates; these consist of a series of bony or cartilaginous cylindrical vertebrae with neural arches that protect the spinal cord, with projections that link the vertebrae. However hagfish have incomplete braincases and no vertebrae, are therefore not regarded as vertebrates, but as members of the craniates, the group from which vertebrates are thought to have evolved; however the cladistic exclusion of hagfish from the vertebrates is controversial, as they ma
Lithobates is a subgenus or genus of true frogs, of the family Ranidae. The name is derived from litho- and the Greek bates, meaning one that treads on rock, or rock climber; the name was defined by Hillis and Wilcox for a subgenus of four Central and South American frogs within the genus Rana: The subgenus was subsequently expanded to seven species in Central and South America in a systematic revision of the genus Rana. The name was used by Frost et al. as a separate genus of ranid frogs that included most of the North American frogs traditionally included in the genus Rana, including the American bullfrog and northern leopard frog. Frost used the name in this sense in the frog section of a North American common names list edited by Crother; this proposed change has since been rejected by others, such as Pauly et al.. AmphibiaWeb, Yuan et al.. AmphibiaWeb, available at http://amphibiaweb.org/, an online compendium of amphibian names, follows Yuan et al. in recognizing Lithobates as a subgenus.
On the other hand, Amphibian Species of the World 6.0, an online reference, uses Lithobates as a genus. This definition is followed by, e.g. the International Union for Conservation of Nature and the Society for the Study of Amphibians and Reptiles. Following the narrowest definition of Lithobates as a subgenus, this taxon contains these species: Following the Amphibian Species of the World, the genus Lithobates contains these species
A tadpole is the larval stage in the life cycle of an amphibian that of a frog or toad. They are wholly aquatic, though some species have tadpoles that are terrestrial; when first hatched from the egg they have a more or less globular body, a laterally compressed tail and internal or external gills. As they grow they undergo metamorphosis, during which process they grow limbs, develop lungs and reabsorb the tail. Most tadpoles are herbivorous and during metamorphosis the mouth and internal organs are rearranged to prepare for an adult carnivorous lifestyle. Having no hard parts, it might be expected. However, traces of biofilms have been preserved and fossil tadpoles have been found dating back to the Miocene. Tadpoles are eaten in some parts of the world and are mentioned in folk tales and used as a symbol in ancient Egyptian numerals; the name "tadpole" is from Middle English taddepol, made up of the elements tadde, "toad", pol, "head". "pollywog" / "polliwog" is from Middle English polwygle, made up of the same pol, "head", wiglen, "to wiggle".
Tadpoles are young amphibians that live in the water, though a few tadpoles are semi-terrestrial and terrestrial. During the tadpole stage of the amphibian life cycle, most respire by means of autonomous external or internal gills, they do not have arms or legs until the transition to adulthood, have a large, flattened tail with which they swim by lateral undulation, similar to most fish. As a tadpole matures, it most metamorphosizes by growing limbs and outwardly absorbing its tail by apoptosis. Lungs develop around the time of leg development, tadpoles late in development will be found near the surface of the water, where they breathe air. During the final stages of external metamorphosis, the tadpole's mouth changes from a small, enclosed mouth at the front of the head to a large mouth the same width as the head; the intestines shorten to accommodate the new diet. Most tadpoles are herbivorous; some species are omnivorous. Tadpoles vary in size, both during their development and between species.
For example, in a single family, length of late-stage tadpoles varies between 33 millimetres and 106 millimetres. The tadpoles of Pseudis paradoxa grow to the largest of any frog. Despite their soft-bodied nature and lack of mineralised hard parts, fossil tadpoles have been recovered from Upper Miocene strata, they are preserved with more robust structures preserved as a carbon film. In Miocene fossils from Libros, the brain case is preserved in calcium carbonate, the nerve cord in calcium phosphate. Other parts of the tadpoles' bodies exist as organic remains and bacterial biofilms, with sedimentary detritus present in the gut. Tadpole remains with telltale external gills are known from several labyrinthodont groups; some tadpoles are used as food. Tadpoles of megophryid frog Oreolalax rhodostigmatus are large, more than 10 cm in length, are collected for human consumption in China. In India, Clinotarsus curtipes are collected for food, in Peru at least Telmatobius mayoloi tadpoles are collected for food and medicine.
According to Sir George Scott, in the origin myths of the Wa people in China and Myanmar, the first Wa originated from two female ancestors Ya Htawm and Ya Htai, who spent their early phase as tadpoles in a lake in the Wa country known as Nawng Hkaeo. In the Ancient Egyptian numerals, a hieroglyphic representing a tadpole was used to denote the value of 100,000. McDiarmid, Roy W.. Tadpoles: the Biology of Anuran Larvae. Chicago: University of Chicago Press. ISBN 0226557634
The true frogs, family Ranidae, have the widest distribution of any frog family. They are abundant throughout most of the world, occurring on all continents except Antarctica; the true frogs are present in North America, northern South America, Europe and Asia. The Asian range extends across the East Indies to New Guinea and a single species has spread into the far north of Australia. True frogs are smooth and moist-skinned, with large, powerful legs and extensively webbed feet; the true frogs vary in size, ranging from small—such as the wood frog —to the largest frog in the world, the goliath frog. Many of the true frogs live close to water. Most species go through a tadpole stage. However, as with most families of frogs, there is large variation of habitat within the family; those of the genus Tomopterna are burrowing frogs native to Africa and exhibit most of the characteristics common to burrowing frogs around the world. There are arboreal species of true frogs, the family includes some of the few amphibians that can live in brackish water.
The subdivisions of the Ranidae are still a matter of dispute, although many are coming to an agreement. Most authors believe the subfamily Petropedetinae is a distinct family called Petropedetidae; the validity of the Cacosterninae is disputed. Still, there is general agreement today that the Mantellidae, which were considered another ranid subfamily, form a distinct family. There is a recent trend to split off the forked-tongued frogs as distinct family Dicroglossidae again. In addition, the delimitation and validity of several genera is in need of more research. Namely, how the huge genus Rana is best split up requires more study. While the splitting-off of several genera—like Pelophylax—is rather uncontroversial, the American bullfrogs separated in Lithobates and groups such as Babina or Nidirana represent far more disputed cases. While too little of the vast diversity of true frogs has been subject to recent studies to say something definite, as of mid-2008, studies are going on, several lineages are recognizable.
Genera such as Nyctibatrachus and Staurois, the complex around Euphlyctis, Nannophrys and the paraphyletic Fejervarya are very ancient offshoots of the main Raninae lineage. Amolops has been delimited as a monophyletic group. Odorrana and Rana plus some proposed minor genera form another group. A group including Clinotarsus, Huia in the strict sense and Meristogenys An ill-defined assemblage of Babina, Hylarana, Pulchrana and Sylvirana, as well as Hydrophylax and Pelophylax, which are not monophyletic. Most of them are now treated as junior synonyms of the genus Hylarana. A number of taxa are placed in Ranidae incertae sedis, that is, their taxonomic status is too uncertain to allow more specific placement. Rhacophorus depressus was included in Ranidae, but has since been given its own family; the subfamilies included under Ranidae, now treated as separate families, are: Ceratobatrachinae Conrauinae Dicroglossinae Micrixalinae Nyctibatrachinae Petropedetinae Ptychadeninae Raninae Ranixalinae Cai, Hong-xia.
Zootaxa 1531: 49–55. PDF fulltext Cogger, H. G.. G.. Fog City Press. ISBN 1-877019-69-0 Frost, Darrel R.: Amphibian Species of the World Version 3 - Petropedetidae Noble, 1931. American Museum of Natural History, New York, USA. Retrieved 2006-AUG-05. Frost, Darrel R. et al.: The amphibian tree of life. Bulletin of the American Museum of Natural History. Number 297. New York. Gordon, Malcolm S.. J. Exp. Biol. 38: 659–678. PDF fulltext Hillis, D. M. Constraints in naming parts of the Tree of Life. Mol. Phylogenet. Evol. 42: 331–338. Doi:10.1016/j.ympev.2006.08.001 PDF fulltext Hillis, D. M.. P.: Phylogeny of the New World true frogs. Mol. Phylogenet. Evol. 34: 299–314. Doi:10.1016/j.ympev.2004.10.007 PDF fulltext Kotaki, Manabu. Zool. Sci. 25: 381–390. Doi:10.2108/zsj.25.381 Pauly, Greg B.. Herpetologica 65: 115-128. Rafinesque, C. S.: "Fine del prodromo d'erpetologia siciliana ". Specchio delle Scienze, o, Giornale Enciclopedico di Sicilia 2: 102-104... Stuart, Bryan L.: The phylogenetic problem of Huia. Mol. Phylogenet. Evol.
46: 49-60. Doi:10
The raccoon, sometimes spelled racoon known as the common raccoon, North American raccoon, northern raccoon, or coon, is a medium-sized mammal native to North America. The raccoon is the largest of the procyonid family, having a body length of 40 to 70 cm and a body weight of 5 to 26 kg, its grayish coat consists of dense underfur which insulates it against cold weather. Three of the raccoon's most distinctive features are its dexterous front paws, its facial mask, its ringed tail, which are themes in the mythologies of the indigenous peoples of the Americas. Raccoons are noted for their intelligence, with studies showing that they are able to remember the solution to tasks for at least three years, they are nocturnal and omnivorous, eating about 40% invertebrates, 33% plants, 27% vertebrates. The original habitats of the raccoon are deciduous and mixed forests, but due to their adaptability they have extended their range to mountainous areas, coastal marshes, urban areas, where some homeowners consider them to be pests.
As a result of escapes and deliberate introductions in the mid-20th century, raccoons are now distributed across much of mainland Europe and Japan. Though thought to be solitary, there is now evidence that raccoons engage in gender-specific social behavior. Related females share a common area, while unrelated males live together in groups of up to four animals to maintain their positions against foreign males during the mating season, other potential invaders. Home range sizes vary anywhere from 3 hectares for females in cities to 5,000 hectares for males in prairies. After a gestation period of about 65 days, two to five young, known as "kits", are born in spring; the kits are subsequently raised by their mother until dispersal in late fall. Although captive raccoons have been known to live over 20 years, their life expectancy in the wild is only 1.8 to 3.1 years. In many areas and vehicular injury are the two most common causes of death; the word "raccoon" was adopted into English from the native Powhatan term, as used in the Colony of Virginia.
It was recorded on John Smith's list of Powhatan words as aroughcun, on that of William Strachey as arathkone. It has been identified as a reflex of a Proto-Algonquian root *ahrah-koon-em, meaning " one who rubs and scratches with its hands". Spanish colonists adopted the Spanish word mapache from the Nahuatl mapachtli of the Aztecs, meaning " one who takes everything in its hands". In many languages, the raccoon is named for its characteristic dousing behavior in conjunction with that language's term for bear, for example Waschbär in German, Huan Xiong in Chinese, orsetto lavatore in Italian, araiguma in Japanese. Alternatively, only the washing behavior might be referred to, as in Russian poloskun; the colloquial abbreviation coon is used in words like coonskin for fur clothing and in phrases like old coon as a self-designation of trappers. In the 1830s, the United States Whig Party used the raccoon as an emblem, causing them to be pejoratively known as "coons" by their political opponents, who saw them as too sympathetic to African-Americans.
Soon after that the term became an ethnic slur in use between 1880 and 1920, the term is still considered offensive. In the first decades after its discovery by the members of the expedition of Christopher Columbus, the first person to leave a written record about the species, taxonomists thought the raccoon was related to many different species, including dogs, cats and bears. Carl Linnaeus, the father of modern taxonomy, placed the raccoon in the genus Ursus, first as Ursus cauda elongata in the second edition of his Systema Naturae as Ursus Lotor in the tenth edition. In 1780, Gottlieb Conrad Christian Storr placed the raccoon in its own genus Procyon, which can be translated as either "before the dog" or "doglike", it is possible that Storr had its nocturnal lifestyle in mind and chose the star Procyon as eponym for the species. Based on fossil evidence from Russia and Bulgaria, the first known members of the family Procyonidae lived in Europe in the late Oligocene about 25 million years ago.
Similar tooth and skull structures suggest procyonids and weasels share a common ancestor, but molecular analysis indicates a closer relationship between raccoons and bears. After the then-existing species crossed the Bering Strait at least six million years in the early Miocene, the center of its distribution was in Central America. Coatis and raccoons have been considered to share common descent from a species in the genus Paranasua present between 5.2 and 6.0 million years ago. This assumption, based on morphological comparisons of fossils, conflicts with a 2006 genetic analysis which indicates raccoons are more related to ringtails. Unlike other procyonids, such as the crab-eating raccoon, the ancestors of the common raccoon left tropical and subtropical areas and migrated farther north about 2.5 million years ago, in a migration, confirmed by the discovery of fossils in the Great Plains dating back to the middle of the Pliocene. Its most recent ancestor was Procyon rexroadensis, a large Blancan raccoon from the Rexroad Formation characterized by its narrow back teeth and large lower jaw.
As of 2005, Mammal Species of the World recognizes 22 subspecies of raccoons. Four of these subspecies living only on small Central American and Caribbean islan